Optical resonant absorption and third-order nonlinearity of (Au,Ag)–TiO2 granular composite films

The nanosized (Au,Ag)–Ti three-component granular composite films on glass substrates were prepared using an rf co-sputtering method, and the deposited films were annealed in air. The optical absorption and the ultrafast third-order nonlinearity of the (Au,Ag)–TiO2 films annealed at different temperatures were investigated. The composite film annealed at 600°C exhibits strong resonant absorption at wavelengths of 400 and 670 nm. The ultrafast third-order nonlinear optical susceptibility at 820 nm of the phase separated (Au,Ag)–TiO2 composite film is measured to be 7.4 × 10−9 esu. This is about 70% larger than that of the Au–TiO2 composite film.